Disk drive detecting mini wedge by evaluating wedge ID of servo sector
A disk drive is disclosed comprising a head actuated over a disk comprising a plurality of tracks defined by servo sectors forming a plurality of full wedges and a plurality of mini wedges. The wedge ID field of a servo sector forming one of the full wedges is offset from a beginning of a sync mark by a first offset, and the wedge ID field of a servo sector forming one of the mini wedges is offset from the beginning of the sync mark by a second offset equal to the first offset. A first servo sector is read from the disk to generate a read signal, the read signal is demodulated to detect the wedge ID of the first servo sector, and the detected wedge ID is evaluated to determine whether the first servo sector forms one of the mini wedges.
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This application claims the benefit of U.S. Provisional Application No. 61/917,875, filed on Dec. 18, 2013, which is hereby incorporated by reference in its entirety.
BACKGROUNDDisk drives comprise a disk and a head connected to a distal end of an actuator arm which is rotated about a pivot by a voice coil motor (VCM) to position the head radially over the disk. The disk comprises a plurality of radially spaced, concentric tracks for recording user data sectors and servo sectors. The servo sectors comprise head positioning information (e.g., a track address) which is read by the head and processed by a servo control system to control the actuator arm as it seeks from track to track.
In the embodiment of
In the embodiment of
By recording the wedge ID field with the same offset from the beginning of the sync mark for both a full wedge and a mini wedge, when the head reads a mini wedge the wedge ID field may be demodulated as if it were in a full wedge. That is, the demodulated wedge ID would include the bits of the mini wedge ID (W_ID) plus a number of bits that extend into the track ID field in the example of
An example embodiment of recording the wedge ID in a manner that distinguishes a full wedge from a mini wedge is illustrated in the partial wedge ID table shown in
The embodiment of
Another example embodiment of recording the wedge ID in a manner that distinguishes a full wedge from a mini wedge is illustrated in the partial wedge ID table shown in
The embodiment of
Another example embodiment of recording the wedge ID in a manner that distinguishes a full wedge from a mini wedge is illustrated in the partial wedge ID table shown in
The embodiment of
Although the example embodiments described above encode the wedge ID using 9 bits, the wedge ID may be encoded using any suitable number of bits in order to encode any suitable number of wedges. In addition, the wedge ID of a servo sector in a mini wedge may represent any suitable number of most significant bits of the recorded wedge ID. For example, the wedge ID of a mini wedge servo sector may comprise a single bit or more than the two bits described in the above embodiments. In addition, there may be more or less than three mini wedges between each full wedge as in the above described embodiments. In the embodiments described above where the wedge ID may be shifted right before recording the wedge ID on the disk, the wedge ID may be shifted right any suitable number of times. Still further, the binary bits of the wedge ID recorded in a servo sector of a mini wedge may be encoded in any suitable manner in order to represent any suitable aspect of a mini wedge, such as a mini wedge that precedes a full wedge or a sequence of mini wedges.
Any suitable control circuitry may be employed to implement the flow diagrams in the above embodiments, such as any suitable integrated circuit or circuits. For example, the control circuitry may be implemented within a read channel integrated circuit, or in a component separate from the read channel, such as a disk controller, or certain operations described above may be performed by a read channel and others by a disk controller. In one embodiment, the read channel and disk controller are implemented as separate integrated circuits, and in an alternative embodiment they are fabricated into a single integrated circuit or system on a chip (SOC). In addition, the control circuitry may include a suitable preamp circuit implemented as a separate integrated circuit, integrated into the read channel or disk controller circuit, or integrated into a SOC.
In one embodiment, the control circuitry comprises a microprocessor executing instructions, the instructions being operable to cause the microprocessor to perform the flow diagrams described herein. The instructions may be stored in any computer-readable medium. In one embodiment, they may be stored on a non-volatile semiconductor memory external to the microprocessor, or integrated with the microprocessor in a SOC. In another embodiment, the instructions are stored on the disk and read into a volatile semiconductor memory when the disk drive is powered on. In yet another embodiment, the control circuitry comprises suitable logic circuitry, such as state machine circuitry.
The various features and processes described above may be used independently of one another, or may be combined in various ways. All possible combinations and subcombinations are intended to fall within the scope of this disclosure. In addition, certain method, event or process blocks may be omitted in some implementations. The methods and processes described herein are also not limited to any particular sequence, and the blocks or states relating thereto can be performed in other sequences that are appropriate. For example, described tasks or events may be performed in an order other than that specifically disclosed, or multiple tasks or events may be combined in a single block or state. The example tasks or events may be performed in serial, in parallel, or in some other manner. Tasks or events may be added to or removed from the disclosed example embodiments. The example systems and components described herein may be configured differently than described. For example, elements may be added to, removed from, or rearranged compared to the disclosed example embodiments.
While certain example embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions disclosed herein. Thus, nothing in the foregoing description is intended to imply that any particular feature, characteristic, step, module, or block is necessary or indispensable. Indeed, the novel methods and systems described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the methods and systems described herein may be made without departing from the spirit of the embodiments disclosed herein.
Claims
1. A disk drive comprising:
- a disk comprising a plurality of tracks defined by servo sectors forming a plurality of full wedges and a plurality of mini wedges, wherein: each servo sector comprises a sync mark and a wedge ID field for storing a wedge ID identifying one of the wedges; the wedge ID field of a servo sector forming one of the full wedges is longer than the wedge ID field of a servo sector forming one of the mini wedges; the wedge ID field of a servo sector forming one of the full wedges is offset from a beginning of the sync mark by a first offset; and the wedge ID field of a servo sector forming one of the mini wedges is offset from the beginning of the sync mark by a second offset equal to the first offset;
- a head actuated over the disk; and
- control circuitry configured to: read a first servo sector from the disk to generate a read signal; demodulate the read signal to detect the wedge ID of the first servo sector; and evaluate the detected wedge ID to determine whether the first servo sector forms one of the mini wedges.
2. The disk drive as recited in claim 1, wherein the control circuitry is further configured to determine whether the first servo sector forms one of the mini wedges by evaluating at least one high order bit of the detected wedge ID.
3. The disk drive as recited in claim 1, wherein the control circuitry is further configured to determine whether the first servo sector forms one of the mini wedges when the detected wedge ID exceeds a threshold.
4. The disk drive as recited in claim 1, wherein the control circuitry is further configured to evaluate the detected wedge ID to determine whether the first servo sector forms one of the mini wedges that precedes one of the full wedges.
5. The disk drive as recited in claim 4, wherein there are M mini wedges between consecutive full wedges and the control circuitry is further configured to evaluate the detected wedge ID to determine a position of the first servo sector within the M mini wedges.
6. The disk drive as recited in claim 5, wherein when the first servo sector is determined to form one of the full wedges, the control circuitry is further configured to shift the detected wedge ID left at least once to identify the full wedge.
7. The disk drive as recited in claim 1, wherein when the first servo sector is determined to form one of the full wedges, the control circuitry is further configured to shift the detected wedge ID left at least once to identify the full wedge.
8. A method of operating a disk drive, the disk drive comprising a head actuated over a disk comprising a plurality of tracks defined by servo sectors forming a plurality of full wedges and a plurality of mini wedges, wherein: the method comprising:
- each servo sector comprises a sync mark and a wedge ID field for storing a wedge ID identifying one of the wedges;
- the wedge ID field of a servo sector forming one of the full wedges is longer than the wedge ID field of a servo sector forming one of the mini wedges;
- the wedge ID field of a servo sector forming one of the full wedges is offset from a beginning of the sync mark by a first offset; and
- the wedge ID field of a servo sector forming one of the mini wedges is offset from the beginning of the sync mark by a second offset equal to the first offset;
- reading a first servo sector from the disk to generate a read signal;
- demodulating the read signal to detect the wedge ID of the first servo sector; and
- evaluating the detected wedge ID to determine whether the first servo sector forms one of the mini wedges.
9. The method as recited in claim 8, further comprising determining whether the first servo sector forms one of the mini wedges by evaluating at least one high order bit of the detected wedge ID.
10. The method as recited in claim 8, further comprising determining whether the first servo sector forms one of the mini wedges when the detected wedge ID exceeds a threshold.
11. The method as recited in claim 8, further comprising evaluating the detected wedge ID to determine whether the first servo sector forms one of the mini wedges that precedes one of the full wedges.
12. The method as recited in claim 11, wherein there are M mini wedges between consecutive full wedges and the method further comprises evaluating the detected wedge ID to determine a position of the first servo sector within the M mini wedges.
13. The method as recited in claim 12, wherein when the first servo sector is determined to form one of the full wedges, the method further comprises shifting the detected wedge ID left at least once to identify the full wedge.
14. The method as recited in claim 8, wherein when the first servo sector is determined to form one of the full wedges, the method further comprises shifting the detected wedge ID left at least once to identify the full wedge.
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Type: Grant
Filed: Jan 10, 2014
Date of Patent: Oct 6, 2015
Assignee: Western Digital Technologies, Inc. (Irvine, CA)
Inventors: Michael Chang (San Jose, CA), Wei Guo (Fremont, CA), Russ A. Quisenberry (San Jose, CA), Guoxiao Guo (Irvine, CA)
Primary Examiner: Daniell L Negron
Application Number: 14/152,737
International Classification: G11B 5/596 (20060101); G11B 20/12 (20060101); G11B 20/10 (20060101);